The Hishikari gold deposit was discovered by the Metal Mining Agency of Japan in 1981. Subsequent exploration and development by Sumitomo Metal Mining Co., Ltd.(SMM), the property owner, have proved Hishikari to be one of the outstanding gold deposits in the Japanese mining history.
The main obstacle to development was a large amount of hot water with a temperature of 60-65°C within the veins, of which original static water level was 100m above the upper limit of vein systems. A carefully arranged program which included a series of grout to fractures, a set of special valves and gates for unexpected outflow of hot water under pressure and a considerable modification to scale free dewatering operation Inade it possible to access the ore body at 100MLin July, 1985 when the mine started production at the rate of 200 t/d.
Other problem was a shortage of skilled underground workers because SMM had closed all domestic mines by 1979. In cooperation with subsidiary companies who kept mining people after the mine closure, OJT (on-thejob training) to local young and unexperienced workers was a key factor for successful development and initial stage of operation, by which the initial capital investment was paid back within two years from the start of production on simple calculation.
Recent economic circumstances, especially declining gold price by the exchange rate of yen to dollar, forced Hishikari to expand its production rate and improve operation process. The discovery of two new ore bodies in the adjacent area and the improvement of operation process enabled to expand its production rate to 150, 000t/y (555t/d) at the end of September, 1992.
Although these improvement will contribute to effective mine operation for the time being, new challenge and continuous efforts will be essential for future operation.